An invasive alga species native to Asia has been documented in the Great South Bay and elsewhere on Long Island’s shores, turning the water red and creating surreal scenes where it’s washed up along ice-logged waterways.

Ranging in color from orange to pink to reddish brown, depending on its health, the alga has a delicate, branching form that it loses out of water.

It’s not harmful to humans but can reduce oxygen levels in water when it dies out. It can also take in nutrients relied upon by other native species, reducing the diversity of local species.

Scientists affiliated with Stony Brook University, including Dr. Rebecca Grella (pictured), have identified a new form of algae on Long Island, Jan. 30, 2018. Photo Credit: Johnny Milano

The alga is usually found in shallow waters 10- to 15-feet deep and can be fragile, dying out and rising to the surface as seasons change, said Craig W. Schneider, a biology professor at Trinity College in Connecticut.

“It’s not toxic,” said Schneider, who was among the first to document the species in the region’s water when it appeared in Rhode Island in 2007. “It’s a pest more than it is a severe problem.”

Native to Asian Pacific waters, the fast-growing and mobile alga known as Dasysiphonia japonica gained a hold in Europe before hitting the Northeast, perhaps hitching a ride in the ballast of a ship or attached to a hull.

“It’s pushed its way all the way down to New York City,” Schneider said. “We got invaded by an invasive.”

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The species can be found in sandy and rocky areas and survives in temperatures between 32 degrees and 86 degrees farenheit. It can attach to rocks, seaweed and other organisms or be free-floating, according to a 2013 report in the journal BioInvasions Records. Like other algae, it thrives in nitrogen-rich waters.

Many Long Island waterbodies have high nitrogen levels fed by road runoff, wastewater and other factors and the region has struggled with algal blooms for decades. Red, brown, blue-green, rust, mahogany tides — some dangerous, some not — have been documented in Nassau and Suffolk counties.

Studies show the invasive species can consume nutrients faster than others and when it is abundant the diversity of other fauna present reduces.

Stephen Borghardt, a director with the nonprofit environmental group Save the Great South Bay, first noticed it on New Year’s Eve at a marina in Blue Point when the region was in a deep freeze.

Some was encased in ice, other pieces were draping the shore, covering rocks, sand and plants in a soupy red.

“I had seen this pinkish, reddish hue in the ice,” said the Bay Port resident. “I thought someone had dropped antifreeze, it was that bright.”

He took some pictures.

“It almost looks like something out of a heavy metal album cover,” he said.

Adding to the scene was a sickening smell of rotten eggs coming from the dying or dead algae.

So Borghardt took his unusual find to social media and posted on his group’s Facebook page.

That led to Dianna K. Padilla, a Stony Brook University professor in the department of ecology and evolution, and Rebecca Grella, director of science research for Brentwood High School who is also an affiliate at Padilla’s Lab.

Grella got Borghardt to take some samples and she went looking also, finding some of the alga in Northport Harbor and near Crab Meadow Beach. “It actually looked like the ice was bleeding red,” Grella said.

Samples shipped off to the University of Rhode Island confirmed the identity of the alga, which Grella calls “Dasy” for short.

It’s hard to know how prevalent it is because no formal effort to monitor Long Island’s coasts and waterway for invasive species is in place, Padilla said.

“We have no idea of the non-native species that are here or where they are on Long Island,” Padilla said.

DEC spokesman Sean Mahar said the agency was not aware of the alga find until contacted by Newsday.

As part of the state’s Ocean Action Plan, which was finalized in January 2017, the agency is developing an aquatic monitoring program but it is not yet active, he said.

Currently, the DEC works with other groups, organizations and volunteers to respond to reports of unfamiliar species. One, the state’s Long Island Invasive Species Management Area, focuses on fostering diversity of local species and reducing invasive species. It’s in the process of hiring new staff and one priority will be on aquatic monitoring, said Polly Weigand, executive director of the Long Island Native Plant Initiative Inc., which oversees the local management area program.

Invasive species in the water are harder to spot than those on land, often requiring scuba gear and underwater mapping.

“It’s a silent invasion,” Weigand said. “It’s not as easy to see and detect as it is in terrestrial ecosystems.”

Still, with sightings on the north and south shores, the scientists said the invasive alga is likely all over Long Island’s coastal areas.

“We’re going to be doing further exploration over the next several months to look around Long Island to see how widespread it is,” Padilla said.

Dasysiphonia japonica was first seen locally in Southold in 2009 but no efforts were made to monitor it.

Great Atlantic Shellfish Farms President Douglas Winter Sr. first noticed the alga in 2014 when some got sucked into equipment that pulls in water from Great South Bay for his clam and oyster hatchery in East Islip.

It’s not fatal to hard shells but “it just kind of fouls up the gear,” he said.

To some, the colorful alga is pretty. A lab assistant at Winter’s hatchery took samples and used them to make art. And at Grella’s lab at Brentwood’s Sonderling High School, students mused about using it to help create a hair dye.